1. Field of the Invention
The present invention relates to a tetramethyltetrahydronaphthalene purification process, and more particularly, to a process for the removal of by-products from a tetramethyltetrahydronaphthalene product mixture.
2. Description of the Prior Art
1,1,4,4-tetramethyl-1,2,3,4-tetrahydronaphthalene (TMT) can be prepared by first converting commercial 2,5-dimethyl-2,5-hexanediol to 2,5-dichloro-2,5-dimethylhexane by reaction with hydrogen chloride. The 2,5-dichloro-2,5-dimethylhexane is then reacted with excess benzene in the presence of aluminum chloride to yield TMT and a bis cyclialkyl product. Upon prolonged contact with the catalyst and benzene, the bis cyclialkyl product is also converted to TMT. The reaction mixture can be purified to some extent by distillation.
While the foregoing process for producing TMT can result in distilled yields in the range of from about 70 to about 75 mole percent TMT based on the diol starting material, the distilled reaction mixture contains, among other by-products, undesirable aromatic hydrocarbon compounds.
TMT is particularly useful and has achieved favor as an intermediate to a number of perfume fragrances. However, if the TMT product includes by-product amounts or aromatic hydrocarbon compounds, particularly dihydronaphthalenes and indenes, as do both the crude and distilled reaction product mixtures produced as described above, it is generally unacceptable as an intermediate for use by the perfume industry.
Thus, there is a need for a process for producing a purified TMT mixture which does not include objectionable aromatic hydrocarbon compounds.